This application is related to application Ser. No. 550,376, entitled: "KEY ASSEMBLY FOR VEHICLE ANTI-THEFT SECURITY SYSTEM", filed by J. Edgar on July 10, 1990 and assigned to the assignee of the subject invention.
This invention is related generally to a method and apparatus for making a key assembly having an integral electrical resistor and is specifically directed to a method and apparatus for mechanically securing a resistor pellet in a mechanical key.
The development of numerous different electronics Vehicle Anti-Theft Security (VATS) systems for an automobile has taken place over the years. One such system incorporates the use of a resistor pellet in an ignition key, as shown in co-pending application U.S. Ser. No. 550,376. As there shown, a resistor pellet is provided in a typical mechanical ignition key, the pellet providing for a resistor of known resistance value so that upon insertion and rotation of the key in an automobile ignition cylinder, an electrical current is applied to and through the resistor. A decoding circuit performs a resistance comparison between the pellet in the key and a known resistance "window" in the circuit. If the resistance is within the window, the automobile may be started. If the resistance does not match the "window" value, the automobile will not start.
It is known to provide attachment of the resistance pellet to the key by sonic welding techniques or by use of adhesives. A disadvantage with either of these methods is that flashing, caused by sonic welding, or over-application of adhesive can cover or partially obstruct the exposed metal surface contacts of the resistor element embedded in the plastic pellet. If the contacts become obstructed, the resistance value of the pellet may be misread by the decoding circuit, rendering the key inoperative.
Use of adhesives or sonic welding are also disadvantageous in that it is required that the key member and the pellet be free of contaminants in order to assure a good bond between the key and the pellet. Dust, oil, humidity and other contaminants interfere with proper bonding, sometimes resulting in a weakened bond between the key and the pellet.
Further, the precision alignment of the pellet in the key is far more critical when either sonic welding or adhesive techniques are used to secure and bond the pellet in the key.
Due to the various disadvantages of the bonding techniques of the prior art, it is required that the manufacturing processes carefully control the exposure of the key and the pellets to various contaminants, and further that the resistance value of the pellet be reconfirmed for proper resistance level once the key and the pellet have been assembled.